The present invention relates to a substrate placing stage, more specifically, to a method of fabricating a substrate placing stage having a structure of joining a ceramic base and a cooling member together.
Conventionally, the semiconductor fabricating process uses various substrate placing stages such as ceramic heaters or electrostatic chucks for placing semiconductor wafers.
For example, a ceramic heater or an electrostatic chuck is structured to embed an electrode in the form of a wire, a plate or a film inside a discoid ceramic base corresponding to the shape of a wafer. This is used to set the substrate to a predetermined temperature or to fix the wafer on the substrate placing stage by adsorption utilizing the Coulomb force or the Johnson-Rahbek force.
Recently, the semiconductor etching process and the like include the proposed so-called low-temperature etching process. In this process, for the purpose of further improving an etching selection ratio and an aspect ratio of an etching shape, etching is performed while cooling the wafer at the same time. In addition thereto, in various thin-film processes or in the characteristic evaluation of the substrate, there are increasingly more processes which require the cooling of the wafer. Even when used in a process at a high temperature, it is desirable to add a cooling function to the substrate placing stage so as to restitute the temperature of the substrate back to a room temperature in a shorter time.
To meet such demands, a specific substrate placing stage has been disclosed (in Japanese Unexamined Patent Publication No. 11(1999)-163109, col. 0017, etc.). The substrate placing stage uses a base body made of a composite material containing ceramic and metal as a heat sink. The base body is joined by brazing solder to a ceramic base as the substrate placing stage by use of brazing filler metal. The composite material provides a lower thermal expansion coefficient as compared to a metallic material and also has fine workability.